Daily Report for 21st March 2021

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Measure Value (anomaly) Time Month cumul. Record High Record Low
Minimum Temperature 4.1 °C (+0.1) 23:32 3.7 °C (+0.4) 9.3 °C (+5.3), 2019 -0.7 °C (-4.7), 2018
Maximum Temperature 10.9 °C (+0.1) 12:53 9.2 °C (-0.7) 15.6 °C (+4.8), 2012 6.3 °C (-4.5), 2013
Mean Temperature 7.8 °C (+0.1) 6.5 °C (-0.1) 11.9 °C, 2019 3.5 °C, 2013
Minimum Humidity 63% 12:51 67% 73%, 2019 32%, 2020
Maximum Humidity 87% 07:01 90% 97%, 2010 77%, 2012
Mean Humidity 77% 80% 81%, 2019 58%, 2017
Minimum Pressure 1029 hPa 02:54 1019 hPa 1033 hPa, 2011 999 hPa, 2014
Maximum Pressure 1031 hPa 10:22 1027 hPa 1036 hPa, 2011 1008 hPa, 2014
Mean Pressure 1030 hPa 1023 hPa 1034 hPa, 2011 1005 hPa, 2014
Mean Wind Speed 3.4 mph (-1.8) 5.2 mph (+0.0) 9.0 mph, 2020 2.5 mph, 2011
Maximum Wind Speed 12.0 mph 09:36 13.9 mph 21.5 mph, 2014 8.1 mph, 2011
Maximum Gust 19.4 mph 08:43 21.0 mph 34.6 mph, 2020 10.7 mph, 2011
Mean Wind Direction NNE
Rainfall 0.0 mm 17.7 mm (62%) 2.4 mm, 2014
Maximum Hourly Rain n/a 2.4, 2014
Maximum 10-min Rain n/a 1.5, 2014
Maximum Rain Rate n/a 18, 2014
Minimum Dew Point 1.5 °C 22:00 1.0 °C 7.1 °C, 2019 -6.5 °C, 2020
Maximum Dew Point 5.3 °C 00:32 5.4 °C 10.1 °C, 2019 0.6 °C, 2013
Mean Dew Point 4.0 °C 3.2 °C 8.7 °C, 2019 -1.0 °C, 2013
Measure Value Time Month cumul. Record High Record Low
Night Minimum (21-09) * 6.6 °C * 04:13 4.1 °C 9.3 °C, 2019 -0.7 °C, 2018
Day Maximum (09-21) 10.9 °C 12:54 9.2 °C 15.6 °C, 2012 6.3 °C, 2013
Max 10m Temp Rise 0.5 °C 09:57 0.5 °C 0.8 °C, 2014 0.4 °C, 2013
Max 1hr Temp Rise 1.1 °C 10:12 1.4 °C 2.8 °C, 2012 0.9 °C, 2015
Max 1hr Hum Rise 6% 20:36 7% 17%, 2020 3%, 2019
Max 10m Temp Fall 0.4 °C 19:35 0.5 °C 0.8 °C, 2014 0.2 °C, 2013
Max 1hr Temp Fall 2.0 °C 20:24 1.5 °C 2.3 °C, 2016 0.8 °C, 2013
Max 1hr Hum Fall 7% 09:04 8% 23%, 2020 6%, 2019
Max 10m Wind Speed 9.7 mph 10:16 10.4 mph 15.8 mph, 2020 5.6 mph, 2011
Minimum Feels-like 3.4 °C 08:00 0.3 °C 6.8 °C, 2019 -3.6 °C, 2018
Maximum Feels-like 10.9 °C 12:49 9.2 °C 15.7 °C, 2019 5.0 °C, 2013
Mean Feels-like 6.6 °C 4.7 °C 12.2 °C, 2019 0.7 °C, 2013
Air-frost Hrs 0 hrs 0.1 hrs 5 hrs, 2018 0 hrs, 2009
Measure Value (anomaly) Month cumul. Record High Record Low
Temperature Range 6.8 °C (+0.0) 5.6 °C (-1.0) 14.9 °C (+8.1), 2009 4.0 °C (-2.8), 2015
Humidity Range 24% 23% 53%, 2020 16%, 2019
Pressure Range 2 hPa 8 hPa 14 hPa, 2010 2 hPa, 2021
Measure Value [% of max] Month cumul. Record High Record Low
Sun Hours 1 [9%]49 hrs (70%) [23%] 10.9 [100%], 2009 0 [0%], 2015
Wet Hours 023 hrs (64%) [4.6%] 1, 2014 , 2009
Cloud Cover am: Mostly Cloudy
pm: Overcast
Events None
Comments -
Extra Comments
Issues None known
Observer Absent? Yes - observations may be unreliable
Pond Temperature (Heath) 4.5 °C
Notes
Times of extremes are computed using the midpoint of the longest continuous period at that extreme value.
Cumulative anomalies are reported according to the expected value for the month-to-date rather than month-end.
Sun hrs are initially pulled from the official weather station at Heathrow, and later adjusted by hand to reflect local conditions based on webcam observations. Wet hrs are dervied algorithmically from rainfall data, though may be adjusted manually. Cloud cover and Events are manually reported, often with multi-week delays.
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Daily Graph of Conditions

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Webcam Summary of Cloud Conditions

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